Questions & Answers
What is a boil water order?
Public health officials issue a Boil Water Order when there is a concern that a disaster or other event has the potential to contaminate the water supply. Boiling your water is a proven way to ensure that your water is safe to drink. When a Boil Water Order is issued, you should make sure that any water used for drinking is boiled at least three minutes (five minutes at higher altitudes) to make sure that the water is safe. If you still have power, refrigerate the water after boiling.
How can a cross-connection result in pollution of treated drinking water?
A plumbing system cross-connection is any existing or potential link between a potable (drinking) water supply and any non-potable fluid. Any sudden loss of pressure on the supply line can cause the contaminated fluid to be back-siphoned into the treated water supply. Most connections to individual houses now have devices installed at the water meter to prevent contaminated water from an individual house from being pulled back into the potable water supply. Hoses in containers of toxic chemicals have sometimes sucked the entire contents of the container back into a well when the pump shut off and there was no check valve to prevent back flow.
Does the quality of drinking water in a distribution system tend to degrade over time?
Yes. The quality of treated drinking water does begin to change to a certain amount as soon as it leaves the water treatment plant. Reactions over time in the treated water and between the treated water and the matter it comes in contact with during distribution are continually occurring, and this can decrease the quality of the water. Typical parameters indicating water quality changes in distribution systems include: reduced chlorine residual, increase in heterotrophic plate count, changes in pH, increased turbidity, increases in taste and/or odor problems, and increases in disinfection byproducts.
How does a Consumer Confidence Report (CCR) get distributed to the public?
One copy of the report must be mailed to each customer, unless the governor of a state has waived the mailing requirement for community water systems serving fewer than 10,000 persons. Systems for which the mailing requirement has been waived must: inform their customers that the report will not be mailed; publish the report in one or more local newspapers serving the area in which the system is located; and make the reports available to the public upon request. A further exception may apply to systems serving 500 or fewer persons. These systems may forego publication of the report in a local newspaper if they provide notice by mail, door-to-door delivery, or posting in an appropriate location that the report is available.
Is community water fluoridation a cost-effective method for disease prevention?
Yes. In 1999, an estimated $56 billion was spent nationally on dental services, representing about 5.6 percent of all expenditures for personal health care in the U.S. during that year. The national average cost to restore one cavity with dental amalgam is roughly $65—the approximate cost of providing fluoridation to an individual for a lifetime.
How can nitrifying bacteria cause problems in a municipal water distribution system?
These bacteria change ammonia and other reduced forms of nitrogen to nitrate in water and moist soil environments where oxygen is present. If present in treated drinking water, these microbes can cause problems in those distribution systems where chloramines are used for disinfection. Partial or incomplete nitrification may produce excess nitrite, which accelerates the breakdown of chloramines and reduces the effectiveness of the disinfection process. There is also some concern for potential production of secondary amines and nitrosoamines, a chemical group considered carcinogenic to humans.
Other than preventing the frequent occurrence of stagnant water, what are some of the other advantages of having a looped distribution system instead of dead-end distribution lines?
In the looped system, water can flow from more than one direction when a high rate is required. A fire-flow demand or large-demand use on a dead-end main can only draw water through a single line, and the flow may be further restricted by the line length and pipe size. When repairs are made on a dead-end line, the entire line has to be taken out of service, which, without a bypass system, may mean that customers will be out of water for a while and affected hydrants will hold little or no water for fire protection. Also, the frequent flushing required to maintain water quality on dead-end systems can be an excessive use of water, especially where drought is taking its toll, or supply is at a premium.
How many types of drinking water customer categories are there for a community water system?
The four basic types of customers for community drinking water systems include residential, commercial, industrial and institutional. However, there are numerous subtypes. For example, a public school system is an institutional subtype and a hospital is another. It is not unusual for a consumer subtype to have its own public water system. For example, an interstate highway rest stop or a school system could have their own system. This however, does not exempt them from meeting specific drinking water standards.
Can distribution line flushing cause water quality problems?
Yes, especially if flushing has not been performed properly. The flushing of dead-ends can lead to dirty water complaints if sediment is stirred up and the line has not been flushed enough to fully purge the materials. The flushing velocity should be adequate to suspend loose sediment within the plumbing system and should continue until the water has cleared and disinfectant residual has reached normal expected levels.
What is a normal rate of unaccounted for water loss from a public water system?
In a properly managed system, you can expect to have a 10 to 15 percent unaccounted for water loss from un-metered uses, leaks, etc. If this value exceeds 20 percent, utility managers need to become more concerned about illegal uses and leaks. Periodic audits are recommended for all systems.
Are there any benefits to installing automatic hydrant flushing units on water distribution systems?
Yes, most water distribution systems that have installed them like them although they are not completely trouble free. Special flushing units are now available or automatic hydrant flushing attachments that connect to standard fire hydrants are available. Advantages are savings in man-hours and travel expenses going to and from the flushing points within the system. Since the units run on a timer they can be set to flush in the early morning hours without the presence of a work crew. Flushing when water demand is low has a number of advantages to include reducing complaints associated with pressure drop and colored water that customers sometimes experience with daytime flushing
What is the difference between surface and ground water?
Surface water is found over the land surface in streams, ponds, marshes, lakes or other fresh (not salty) water sources. Ground water is water occurring in the zone of saturation in an aquifer or soil. Other than the location, one of the primary differences between surface and ground water is that ground water moves much slower than surface water. This is because ground water experiences far more friction as it moves through the pores in soil than surface water experiences as it flows over the earth's surface. Surface water is more easily contaminated that ground water.
How much does it cost to fluoridate drinking water?
The per person cost of fluoridation varies by the size of the community population. The average cost of providing fluoridated water to communities with more than 20,000 residents is about 50 cents per year. For communities of 10,000 to 20,000 residents, the cost is about $1, and for those living in communities of less than 5,000, the cost is roughly $3 per year.
Is ground water important?
Ground water, which is found in aquifers below the surface of the Earth, is among the nation's most important natural resources. Ground water is the source of about 40 percent of the water used for public supply. It provides drinking water for more than 97 percent of the rural population who do not have access t o public water–supply systems. In addition, between 30 and 40 percent of the water used for agriculture comes from ground water.
What is Nonpoint Source (NPS) pollution?
Nonpoint source (NPS) pollution, unlike pollution from industrial and sewage treatment plants, comes from many different sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away many natural and man-made pollutants, before depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water. These pollutants often include: excess herbicides, fertilizers, and insecticides from agricultural zones and residential areas; oil, grease, and toxic chemicals from urban runoff and energy production; sediment from improperly managed construction sites, crop and forest lands, and eroding stream banks; salt from irrigation practices and acid drainage from abandoned mines; and bacteria and nutrients from livestock, pet wastes, and faulty septic systems. Atmospheric deposition and hydromodification are also sources of nonpoint source pollution. (EPA-841-F-94-005, 1994 ).
What is Cryptosporidium?
Cryptosporidium is a parasite commonly found in lakes and rivers. It enters water supplies through sewage and animal waste. It causes cryptosporidiosis, a gastrointestinal disease. The largest water systems in the country are currently participating in a testing program in which they check their source water for Cryptosporidium each month for 18 months.
What are coliform bacteria?
Coliform bacteria are a class of rod shaped bacteria that can utilize lactose (milk sugar) as a sole food source. Coliform bacteria are found essentially everywhere, in soil, on skin, in lakes, streams, and rivers. Generally speaking, coliform bacteria do not cause disease. The presence of coliform bacteria is used as an indication that other disease causing organisms may be present in drinking water.
What is the earliest record of a civilized society having a sophisticated water and wastewater distribution system?
According to Dr. Jonathan Mark Kenoyer, professor of anthropology at the University of Wisconsin at Madison, the ancient city of Harappa that was located in the Indus Valley of Pakistan had both a city-wide drinking water system and even a city sewer system. This preceded the record of such systems being employed by the Roman Empire by over 2000 years. The Roman facilities were limited primarily to upper-class neighborhoods. According to modern digs in the Indus Valley region of Harappa, the city measured over 350 acres at its prime, was fixed on three large raised mounds, had a supply of wells throughout the city and most houses were equipped with bathing areas, latrines and sewage drains. The sewage drains were linked to mains similar to modern sewer systems of today and eventually emptied outside the city walls. It is believed that the wastewater from the habitation areas was deposited on the surrounding agricultural fields.